Add service use queue group option

src/NATS.Client.Services/NatsSvcConfig.cs

@@ -54,10 +54,16 @@ public NatsSvcConfig(string name, string version)
     public Dictionary<string, string>? Metadata { get; init; }
 
     /// <summary>
-    /// Queue group name. (default: "q")
+    /// Queue group name. (default: "q" unless <see cref="UseQueueGroup"/> is set to <c>false</c>)
     /// </summary>
     public string QueueGroup { get; init; } = "q";
 
+    /// <summary>
+    /// Use a queue group when creating service subscriptions. (default: <c>true</c>)
+    /// Queue group name is defined using <see cref="QueueGroup"/> property.
+    /// </summary>
+    public bool UseQueueGroup { get; init; } = true;
+
     /// <summary>
     /// Stats handler. JSON object returned by this handler will be included in
     /// the service stats <c>data</c> property.

src/NATS.Client.Services/NatsSvcServer.cs

@@ -97,7 +97,7 @@ public async ValueTask StopAsync(CancellationToken cancellationToken = default)
     /// </remarks>
     public ValueTask AddEndpointAsync<T>(Func<NatsSvcMsg<T>, ValueTask> handler, string? name = default, string? subject = default, string? queueGroup = default, IDictionary<string, string>? metadata = default, INatsDeserialize<T>? serializer = default, CancellationToken cancellationToken = default)
     {
-        queueGroup ??= _config.QueueGroup;
+        queueGroup ??= _config.UseQueueGroup ? _config.QueueGroup : null;
         return AddEndpointInternalAsync<T>(handler, name, subject, queueGroup, metadata, serializer, cancellationToken);
     }
 
@@ -331,7 +331,7 @@ public ValueTask AddEndpointAsync<T>(Func<NatsSvcMsg<T>, ValueTask> handler, str
         {
             subject ??= name;
             var epSubject = subject != null ? $"{GroupName}{_dot}{subject}" : null;
-            queueGroup ??= QueueGroup ?? _server._config.QueueGroup;
+            queueGroup ??= QueueGroup ?? (_server._config.UseQueueGroup ? _server._config.QueueGroup : null);
             serializer ??= _server._nats.Opts.SerializerRegistry.GetDeserializer<T>();
             return _server.AddEndpointInternalAsync(handler, name, epSubject, queueGroup, metadata, serializer, cancellationToken);
         }

tests/NATS.Client.Services.Tests/ServicesTests.cs

@@ -383,4 +383,100 @@ public async Task Service_ids_unique()
 
         Assert.Equal(ids.Count, uniqueIds.Count);
     }
+
+    [Fact]
+    public async Task Service_without_queue_group()
+    {
+        await using var server = await NatsServer.StartAsync();
+        var (nats1, proxy) = server.CreateProxiedClientConnection();
+        await using var nats = nats1;
+        var svc = new NatsSvcContext(nats);
+
+        var cts = new CancellationTokenSource(TimeSpan.FromSeconds(60));
+        var cancellationToken = cts.Token;
+
+        // Default with a queue group
+        {
+            await using var s1 = await svc.AddServiceAsync(
+                new NatsSvcConfig("s1", "1.0.0"), // default is { UseQueueGroup = true },
+                cancellationToken: cancellationToken);
+
+            await using var s2 = await svc.AddServiceAsync(
+                new NatsSvcConfig("s2", "1.0.0"), // default is { UseQueueGroup = true },
+                cancellationToken: cancellationToken);
+
+            await s1.AddEndpointAsync<string>(
+                name: "ep1",
+                handler: async m =>
+                {
+                    await m.ReplyAsync("x", cancellationToken: cancellationToken);
+                },
+                cancellationToken: cancellationToken);
+
+            await s2.AddEndpointAsync<string>(
+                name: "ep1",
+                handler: async m =>
+                {
+                    await m.ReplyAsync("x", cancellationToken: cancellationToken);
+                },
+                cancellationToken: cancellationToken);
+
+            await Retry.Until("subscribed", () => proxy.Frames.Count(f => f.Message.StartsWith("SUB ep1")) == 2);
+
+            var sub = proxy.Frames.First(f => f.Message.StartsWith("SUB ep1")).Message;
+            Assert.Matches(@"SUB ep1 q \d+", sub);
+
+            var count = 0;
+            await foreach (var msg in nats.RequestManyAsync<string, string>("ep1", "x", cancellationToken: cancellationToken))
+            {
+                count++;
+            }
+
+            // Only one reply because of the queue group
+            Assert.Equal(1, count);
+        }
+
+        await proxy.FlushFramesAsync(nats);
+
+        // Without any queue group
+        {
+            await using var s1 = await svc.AddServiceAsync(
+                new NatsSvcConfig("s1", "1.0.0") { UseQueueGroup = false },
+                cancellationToken: cancellationToken);
+
+            await using var s2 = await svc.AddServiceAsync(
+                new NatsSvcConfig("s2", "1.0.0") { UseQueueGroup = false },
+                cancellationToken: cancellationToken);
+
+            await s1.AddEndpointAsync<string>(
+                name: "ep1",
+                handler: async m =>
+                {
+                    await m.ReplyAsync("x", cancellationToken: cancellationToken);
+                },
+                cancellationToken: cancellationToken);
+
+            await s2.AddEndpointAsync<string>(
+                name: "ep1",
+                handler: async m =>
+                {
+                    await m.ReplyAsync("x", cancellationToken: cancellationToken);
+                },
+                cancellationToken: cancellationToken);
+
+            await Retry.Until("subscribed", () => proxy.Frames.Count(f => f.Message.StartsWith("SUB ep1")) == 2);
+
+            var sub = proxy.Frames.First(f => f.Message.StartsWith("SUB ep1")).Message;
+            Assert.Matches(@"SUB ep1 \d+", sub);
+
+            var count = 0;
+            await foreach (var msg in nats.RequestManyAsync<string, string>("ep1", "x", cancellationToken: cancellationToken))
+            {
+                count++;
+            }
+
+            // Two replies because of the absence of any queue groups
+            Assert.Equal(2, count);
+        }
+    }
 }